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(#) Using C2DM

!!! ERROR: Using C2DM
   This is an error.

Id
:   `UsingC2DM`
Summary
:   Using C2DM
Severity
:   Error
Category
:   Security
Platform
:   Android
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   3.3.0 (January 2019)
Affects
:   Manifest files
Editing
:   This check runs on the fly in the IDE editor
See
:   https://developers.google.com/cloud-messaging/c2dm
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/C2dmDetector.kt)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/C2dmDetectorTest.kt)

The C2DM library does not work on Android P or newer devices; you should
migrate to Firebase Cloud Messaging to ensure reliable message
delivery.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
AndroidManifest.xml:7:Error: The C2DM library does not work on Android P
or newer devices; you should migrate to Firebase Cloud Messaging to
ensure reliable message delivery [UsingC2DM]
    &lt;receiver android:name="com.google.android.c2dm.C2DMBroadcastReceiver"&gt;
                            ---------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`AndroidManifest.xml`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers
&lt;manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="test.pkg"&gt;

    &lt;application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" &gt;
        &lt;receiver android:name="com.google.android.c2dm.C2DMBroadcastReceiver"&gt;
          &lt;intent-filter&gt;
            &lt;action android:name="com.google.android.c2dm.intent.RECEIVE"/&gt;
            &lt;action android:name="com.google.android.c2dm.intent.REGISTRATION"/&gt;
        &lt;/intent-filter&gt;
        &lt;/receiver&gt;
    &lt;/application&gt;

&lt;/manifest&gt;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/C2dmDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `C2dmDetector.testPattern1`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=192708.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Adding the suppression attribute `tools:ignore="UsingC2DM"` on the
  problematic XML element (or one of its enclosing elements). You may
  also need to add the following namespace declaration on the root
  element in the XML file if it's not already there:
  `xmlns:tools="http://schemas.android.com/tools"`.

  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;manifest xmlns:tools="http://schemas.android.com/tools"&gt;
      ...
      &lt;receiver tools:ignore="UsingC2DM" .../&gt;
    ...
  &lt;/manifest&gt;
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="UsingC2DM" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'UsingC2DM'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore UsingC2DM ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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